In recent, according to change in the trend of research, there is increasing need of pre-treatment technique such as separation of micro-nano scale particles through microfluidic control of various sample fluids, etc. Particularly, as studies based on microfluidics are diversifying in addition to separation method such as the existing centrifuge requiring for expensive equipment, flow cytometry (FACS), or the like, techniques regarding separation of micro-nano scale particles in microfluidic chip have been actively developed.
Technique of separating micro/nano sized particles has been continuously studied for bioparticle separation for clinical research and biochemical analysis on platelets, circulating tumor cell (CTC), nucleated red blood cell (NRBC), platelet derived microparticle (PDMP) or the like, and nanoparticle separation for analysis of environmental impact of nanoparticles in environment such as air, water, soil, etc.
Among them, control technique of micro-nano scale particles using surface acoustic waves is technique having advantage in that no separate labeling is needed, and the technique is non-invasive and may be driven with low power. Prior research relating to the above-described technique is summarized as below.
U.S. Pat. No. 7,942,568 discloses a micromixer using surface acoustic waves in a microfluidic chip, and the micromixer has advantage in that the micromixer may be easily manufactured, easily combined to the microfluidic chip, and used with low power. The present invention has the same advantage of using surface acoustic waves in a microfluidic chip, but has difference in that the objective of the use of the apparatus is separating micro-nano scale particles.
US Patent Application Publication No. 2010/0139377 discloses an apparatus of focusing micro-nano scale particles using surface acoustic waves in a microfluidic chip, by which micro-nano scale particles may be focused at one or a plurality of pressure nodes formed in a microfluidic channel by surface acoustic waves.
Meanwhile, a thesis of ‘Manipulation of diamond nanoparticles using bulk acoustic waves’ (Journal of applied physics, 109, 014317, 2011) discloses a technique of patterning nanoparticles having a size of 5 nm included in a fluid in a circular or rectangular chamber at a pressure node point formed by surface acoustic waves. Here, patterning of nanoparticles is performed in the chamber, and thus the technique has disadvantage in that the patterning is not performed in continuous flow state of a microfluidic chip. Accordingly, in order to allow for continuous separation of nanoparticles in fluid flow, new type of device has to be developed.
Further, a thesis of ‘Direct visualization of surface acoustic waves along substrates using smoke particles’ (Applied physics letters, 91, 224101, 2007) discloses a technique of patterning and visualizing smoke particles (SP) having a size of 250 nm when surface acoustic waves are transmitted. Here, smoke particles are patterned for 15 to 30 seconds, the patterning is not performed in continuous flow state, and the technique relates to particles floating in the air. However, a technique of separating nano-scale particles with respect to particles floating in the fluid has never been developed.